BobI'm probably a little late on this, but coming to grips with what should be a simple task, like defining "big" in the context of champion tree candidates, has proven not so simple.My thought process has been to begin with my physical approach. In retrospect, every tree that I have encountered as a potential champion candidate was 'big', and reasonably categorized by the trees emergent crown (tree height), and as I got closer, it's trunk (diameter to me is what is visible on approach, not the girth, I know separate argument, but this is still me approaching the champ candidate); and probably the most definitive aspect of a tree's bigness is it's crown. I think we cut the crown short, or at least measure it short...when I was feeding "tree bio-mass" into FARSITE (a fire area growth assimilation program), we took a measure of the crowns portion of the tree, taking readings on base of tree, base of crown, and the tree's top; and an average crown spread (estimates that were challenged WHENEVER a team member disagreed (two-person team).

I'll say this separately for emphasis....for conifers year around, and deciduous trees when leafed out,THE TREE'S CROWN IS FOR ME, OFTEN THE DEFINING "BIGNESS".

In the context of champion tree measurements, I like your walk-around/EXCEL table approach...my only thought on improving it would be the incorporation of the GRS Densitometer in determining the accurate "edge" of the crown.

I hear you. Thinking along the lines that you have communicated, crown spread has played the biggest role for me as well, when viewing a big tree from a distance, and trunk width (diameter) has taken over as I got closer and closer. I suppose that we can always make the argument that crown spread is a surrogate for trunk girth or diameter, but we both know big trees where crown size and trunk size have become mismatched. Crown breakage or crowding has to be figured in to the equation. For the trees that stick out in my mind, height has figured in only when really significant. So, I think we are definitely on the same page.

The Densitometer has been on my list of purchases for a long time. Time for me to move on, get one, and incorporating it in the crown-area measuring process.

Bob

Robert T. LeverettCo-founder and Executive DirectorNative Native Tree SocietyCo-founder and PresidentFriends of Mohawk Trail State Forest

I have pulled the two posts with the Excel workbooks. Alas, they need some serious debugging, especially the second one. I'll re-post them when I've tested them sufficiently and built in error capture routines. I recommend any of you who downloaded the workbook versions I posted, just delete them. Sorry for releasing stuff prematurely.

Bob

Robert T. LeverettCo-founder and Executive DirectorNative Native Tree SocietyCo-founder and PresidentFriends of Mohawk Trail State Forest

I have attached three solutions to computing crown area. All three circumscribe the crown area's drip-line with a polygon. All three methods divide the polygon into a series of adjacent triangles, measure the area of each triangle and sum them. AreaCrownLaserClinometer-1.xlsm measures each side of a triangle to compute its area. The other two method uses azimuths and one distance to calculate the area of a triangle.

There is a fourth computational algorithm that I'll eventually add, which is similar to the second method. Each method has its advantages and disadvantages, which I'll discuss in a future post. I wanted to get these methods posted so Ed can reference them if he needs to in the Wikipedia post he is working on.

The odds are that I haven't completely debugged these methods. Anyone who cares to pitch in and help me test them will earn good karma points.

That's exciting. Thanks for giving the method a test. I think you chose the best one of the three. As soon as this infernal snow melts, I'm going to apply each of the methods to a big spreading hardwood in a nearby park. I need to get a feel for how errors carry through in methods 2 and 3.

BTW, I'm working on a 4th method, which I'll include in a future update. The 4th method allows you to walk the perimeter just shooting distances and azimuths to the next vertex of the polygon. You don't have to shoot to the tree. It doesn't matter what's inside the polygon. However, I think it is harder to control the error in methods 2,3, and 4. Nonetheless, for a very large area where there are obstructions to seeing the trunk, method 4 may be the way to go.

I wish I'd modeled a couple of the big banyans when I was in Hawaii in December. Oh well, there is always next year.

Thanks again for giving the method a test.

Bob

Robert T. LeverettCo-founder and Executive DirectorNative Native Tree SocietyCo-founder and PresidentFriends of Mohawk Trail State Forest

Bob and I have talked about these types of loop traverses as that is what I would do while surveying caves: doing the (x,y ) coordinate positions for each station, calculating closure errors, using front and back sighting to minimize errors etc. You can use error closure routines, but they really don't eliminate the errors just average them across all points so that the loops close. They can be lessened in loops that interconnected in multiple places, but not for single loops like a crown or simple area outline. The loop closure mathematics will actually help if it is a systematic error resulting from a instrument miscalibration. But in reality most errors in these types of surveys are "busts" where most of the data is good and there is a mistake on one reading that accounts for most of the closure error. So various error correction, really error averaging programs, shift all of the points and change the geometric relationships between all of the points in the loop to make up for the one big error. So you introduce error in all of the points in the survey to "fix" error in one measurement. It really doesn't help when trying to measure our crown spread area or other area measurement. The closure error amount will not reflect the area error as the area error will depend on where in the loop the error occurred as well as its magnitude. The best way to minimize error is to make as many of the triangles or polygons within the larger polygon independent so that the error is not propagated, and to take care with the measurements themselves so they are correct and to try to do back sights to confirm the azimuth measurements are correct between points. The inclination errors are less important as we are looking at the area of a flat horizontal polygon, rather than a three dimensional loop, as inclination errors of a degree or so will not significantly affect the horizontal segment length distances.

The links are useful however as they cover the concepts and provides a check on what is being done in our case.

Edward Frank

"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

Doing traverses of caves must be cool! Must quickly get into 3D (x,y,z) I suspect.I mentioned traverses because it's a good layperson method, using basic equipment, and once closures are obtained in the 1:500 or better, they're surely more accurate than our conventional AF-type crown spread measurements, huh? Circling a potential champ once is generally a good idea anyway.